I'm dealing with what is probably air intrusion problem. It's my understanding that the stalling after start condition is caused by fuel draining back into the tank. So far I have not been able to track down where the air is getting in and I'm thinking about going to an electric pump. My other thought is why not put a one way check valve in the fuel line so the fuel does not drain back. They seem to be pretty common on diesels. Has anyone tried this?

 

Have you checked the pressure on your lift pump. If you're having problem with drain back I would say to check press. I know some of the Walbro elec. pumps have built in check valves. The check valves help when your lift is over 3ft. Lift being height from lift pump to IP. You in KC?

 

By the time you come up with a check valve, you could have purchased an EP and totally eliminated fuel drain back. It will also help if you have air intrusion because as soon as you turn the key on the EP will run purging the air while you're waiting on the Wait to Start Light to go out.

It will also help if you run out of fuel. Really saves the starter and batteries.

PS: It's not a good idea to ignore air intrusion. It will end up leaking fuel, making a mess and polluting the environment. Advance Part No. 7135-276 $27.89 will fix the problem.

 

You must drink alot. And that's coming from a guy that drinks alot.

 

I agree that finding the air leak and installing an electric pump are things that should be done. I just went through the process of replacing the return lines only to find the cheap ones I bought were junk and leaked from around the caps badly. I went back to the original caps and it does not leak. I should replace them with a good kit like the Delphi but I don't have a lot of time right now, it's getting cold and my van does not fit in my garage. I only use the van occasionally, mainly to tow my race car so it's not a big deal right now. I ordered a check valve, it should be here in a day or two. It's supposed to be warm the next few days and it should only take a few minutes to install the check valve. The lift pump is fairly new and the pressure and volume seems to be good. It will start after it first starts and stalls but it takes some cranking. Yes I'm in Kansas City.

 

As long as your original return line tees aren't broke Id just keep using them with new orings .

 

What's the fuel level in your tank? There is a common problem with the pickup tube cracking at about the 1/4 way mark. This will cause air in the system.

 

Do you mind if I hijack your thread for a sec?

I got a 6.9 and no wait to start light, I always thought it was the 7.3s way of letting you know the Glow plugs are ready, but after reading this, does it actually have to do with the fact the 7.3s have an electric pump and you are waiting on fuel to be delivered?

Also what are the symptoms of air in the lines (air intrusion)?

I've been told if you are cranking your engine over cold and have no smoke coming from the tailpipe and it won't turn over you have a fuel problem.

Checked mine today after a week with no start and had a buddy watch the exhaust while I tried to start her up and it was probably a good 20 seconds before I had smoke, is this normal on extended cold starts?

[Edit: what's a lift pump?]


Thanks, Sorry,

Devin

PS I will start a new thread if I don't get a quick answer

Thank again

 

Most 7.3 come with a mechanical lift pump. The lift pump is like a normal fuel pump on a gasoline engine, it pulls fuel from the fuel pump and pushes it to the fuel injection pump. Air intrusion is air leaking somewhere into the system. The system is normally all sealed and that keeps fuel from draining back into the fuel tank. If the seal is broken the fuel drains out of the lines and back into tank. When you first crank the engine over the engine will start using the fuel in the injection pump and lines to the injectors and will run for a few seconds but then the air gets to the pump and it stalls. You then have to crank it for a couple of minutes to get fuel to the pump and then it will start. Having a electric pump will pull fuel from the tank to the injection pump without cranking the engine. If your engine will not start first pull the fuel filter and see if its full, or if you have some help crank the engine over with pushing in the valve on the top of the fuel filter housing that looks like a tire valve and fuel should come out. If it does then you probably have glow plug or glow plug relay problems. There are lots of posts on this.

 

Yeah glow plugs/glow plug system is working all correctly.

It doesn't start at all when I go to start her, I suspect there is no fuel being held in my filter or pumps or lines, that's why I have to crank it for awhile.

So your saying there are 3 pumps, fuel pump, lift pump, and injector pump, in that order.

Gonna get the book out now and see what this all looks like.

Devin

 

No, just 2 pumps, a lift pump and the injector pump that sets on top of the engine and has lines running out of it that go to the individual injectors. The fuel filter/water separator is between the lift pump and the injector pump, make sure that it is not clogged or has water in it.

 

If you've checked all possible leaks you can think of,
Top of gas tank sending unit all the way up to the fuel filter, then,...
Place a sheet of paper towels under the injection pump.
There's a tray pan there, run the engine for a while, shut er down and check the paper towel for fuel. If it's wet, your leaking at the IP.
Just another possibility.

 

Thanks Again, continue where you left off

 

I installed a check valve in the rubber line between the input side of the lift pump and the hard line to the fuel pump and it worked like a charm. Starts right up and keeps running after setting overnight. Again its a bit of a hack and I'm planning on figuring out where the air leak is but it works for the time being. I used the 10mm valve.

DIESEL CHECK VALVES

 

That sounds like the check valve inside your fuel pump is no good, why wouldn't you just replace the fuel pump for that price

Airtex Master/Fuel Pump (60278) | 1985 Ford F350 1 ton P/U 4WD 8 Cylinders 1 6.9L Diesel | AutoZone.com_

If my logic is correct, if after adding a check valve at the fuel pump/lift pump and now your truck is working correctly, than that is too assume anything aft of the fuel pump is working correctly also, IE not leaking back into the tank.


Devin